Flashover indicator



y 4, 1954 H. RORDEN ETAL FLASHOVER INDICATOR Filed July 10, 1950 I ATTORNEY ORDEN RBOROUGH HAROLD L. R WILLIAM E. SCA

MERWIN B ELT transmission lines. with means for rindi prior art, some of which resemble the present fiashover indicate Our invention is over other similar devices, partly in mechanical structure and partly inmethod of operation.

the production :simpleandinexpensive, and which will operate Patented May 4, 1954 2,677,817 FLASHOVER INDICATOR .Harold L. Borden, WilliamE.

Merwin B. Elton,

Scarborough, and

Portlan'd,0reg.

Application July 10, 1950, Serial No. 172,994

2 Claims.

(Cl. (Granted under Title 35,

U. S. Code (1952),

see. 266) The invention described herein may be manu- "fa-ctured and used-by or'for the Government of the "United States for governmental purposes =-without th e payment to us of any royalty thereon ancewith the provisions of the act of 1883, (22 Stat. 625), as amended by the act of April 30, 1928, (45 Stat. 467,.35 U. S. C., I

This invention isconc'erned with electric power In particular, it is concerned cating when a tower orpole supporting transmission line conductors has been subjected to flashover.

.iThere are otherfla'shover indicators in the r'in some aspects of operation. concerned with improvements This fiashover indicator is of the type in which operation is accomplished with the release of a signaling device by the ignition of a small charge of explosive powder. The ignitionoccurs when a high-voltage flashover occurs on the line structure .to whichthe indicator is attached.

A .principalobject. of ourfpresent invention is of .a .flashover indicator that is reliably under-Se Another objec cator' that will Vere. service conditions. t is to produce a fiashover indi- 3U operate reliably when infested with vermin such as cocoon-producing larva. Still another obj ect is to provide electrical-"connections for the flashover indicator which will provide reliable operation on either steel or wood towers of transmission lines.

What constitutes our present invention is set forth in the following specification with reference to the drawing and succinctly defined in the appended claims.

In the drawing,

Figure 1 is an elevation showing a front view of a preferred embodiment of our invention mounted with appropriate electrical connections on a wood transmission line pole.

Figure 2 is a partly sectional elevation of the same indicator as shown in Figure 1, but from the back, whereas Figure 1 is a front view.

Figure 3 is a partly sectional view of the same indicator as shown in Figure 2, showing the indicator in position prior to operation; whereas Figure 2 is illustrative of the indicator after operation.

Figure 4 is a partly sectional elevation looking at the left-hand edge in reference to Figure 1.

" surface is provided Figure -5 is an illustration of the mounting of the indicator on asteel tower together with specially applicable electrical connections.

In reference to Figure 1, a flash indicator case i, made of "Bakelite-or similar material is supported on a wood pole 2-which supports transmission conductors in the usual way. Theflash indicator case I is supported'on pole Z'by an' adjustable conducting strap 3 secured by a'bolt 4 which hold also a bracket 5, a flashover rod 6' and an adjusting device 1. Elements 5,"6'and 7 are adopted from the system of lightning grounding on which an application'for patentjNo. 583,483, has been filed by Harold LJ-Rorden.

On pole 2, below the indicator" I, there is a loop of wire 8 which is connectedby a wire 9 to a terminal I i on the side of the indicator. A connection l2, shown'in Figures 2, .3 and 4 on the back of case I; connects strap 3 to the interior of the indicator.

Hinged at one side of case there is an indicating an indicating drop, a circle. On the fa I, near the bottom, closure I4, referred to as of the shape of one-fourth of ce I 5 of drop M, are-fleeting to make the drop easily seen at night when illuminated. by a spot light. The configurationof drop l lis such that when the indicator is set prior'to an indication, "the laterally extending'bottom'ofcase I is closed by'the bottom of indicator M as shown in the section of Figures 3 and 4.

A conducting wire spring [6 is provided to connect strap 1 Ztoa clip I Tinside the indicator for electrical operation and also" to provide a mechanical force on drop it tending toforce the drop open.

Clip I1 holds one end of spring I6 to provide a mechanical rest for the spring pressure as well as electrical contact therewith. Clip H, as usually used in the practical construction of our invention, is an ordinary Fahnstock clip. This form of clip provides a convenient attachment of conductors.

Inside case I on the side With terminal II, a spring latch l8 formed from a resilient metal 3 supported by latch 18, holds drop 14 up in the closed position against the force of spring [6.

Drop 14 is released into the indicating position shown in Figure 2 when link 22 explodes after ignition by any electric impulse of sufficient volt age to jump across the space containing the charge 23 between the inner ends of terminals 2 and 25. In setting the indicator for use, link 22 is inserted in clip l1 and catch I8 is pulled back by tension applied by the attendant on loop l9. Drop M is then pushed up to the closed position and the terminal 2d secured in position above clip 18. When ignited by an electric spark, the charge 23 explodes, bursting link 22 and permitting drop 14 to fall to the position shown in Figure 2. In Figure 2, the remainder of link 22 including the terminal 25 and the adherent remains or the shell of the link 22 is shown held by clip I! in the dropped position after operation.

Referring again to Figure 1, the electrical voltage that explodes link 22 is impressed thereon between strap 3 and wire loop 8. This voltage is conducted by strap 12 from strap 3 to spring l6 through clip IT and terminal 29 to the charge 23, and through terminal 24, clip 18, connection 2|, terminal ii and wire 9 to wire 8. This intallation is characteristic of wood-pole lines in which flashover is to rod 6, usually from the line conductor, through the indicator and down the pole from wire loop 8.

A different way of getting voltage for ignition is used on steel towers as shown in Figure 5. The indicator l is mounted on a steel member 25 of the tower, one leg 21 of which is indicated.

Wire conductors 9 and 28, analogous to conduc- I tor 9 shown in Figure 1, is carried down the tower, for example, down a diagonal member 29. Conductors 9 and 28 are insulated from the tower by insulators 3| or by other conventional means.

Conductor 28 is connected to a ground rod 32 situated near the tower leg footing at which members 2'! and 29 are terminated. Figure 5 does not show the footing details, the drawing extending only to the ground surface 33. The

footings usually are several feet deep and of simi ilar lateral dimensions. The ground rod 32 is placed only sufficiently far from the footing to develop a difference of potential between the ground rod and the footing sufficient to ignite the explosive charge 23. ence is attained, under average fault conditions, when the separation between the ground rod and tower footing is about one foot. It has been found that much greater spacings sometimes pro- This potential differ- 4 duce difference of potentials sufficient to damage the indicator by flashing over between terminal H and other parts inside the case I. The exact spacing under practical conditions needs to be determined by experience.

We claim:

1. In a fiashover indicator the combination of an insulating rectangular case, a hinged bottom in said case with a sector attached to said bottom, arranged to be concealed in said case when said bottom is in the closed position, and visible below said case when said bottom is in the open position, a spring positioned in said case to apply opening pressure to said bottom, a spring pressure clip attached to said bottom and to one end of said spring, a conducting strap on the back of said case for external electrical connection to which the other end of said spring is also connected, a terminal on one side of said case and, connected therewith, a spring catch inside said case, and a flashover by-pass which includes an electrically ignited explosive link held at one end by said spring pressure clip and retained at the other end by said spring catch, said link holding said bottom in the closed position normally and releasing said bottom to the open position when ignited.

2. In a flashover indicator the combination of an insulating case with an indicating bottom drop and closure provided with a reflecting surface, a supporting pivot within said case, said indicating bottom drop and closure being excentrically mounted on said pivot, an explosive drop supporting link in said case, a spring yield ingly forcing said drop against said link, and a. flashover circuit which includes said link, whereby a surge of current in said circuit serves to ignite the explosive of said link permitting gravity and the resilient action of said spring to eject said indicating bottom drop from said case.

References Cited in the file of this patent UNITED STATES PATENTS 

